The Nuffield Trust and the Health Foundation said that there is a "perfect storm" of factors which are leading to an increasing in waiting times in emergency departments across England.

The comments come after the latest figures from NHS England show that major A&E departments failed to treat and discharge or admit 95% patients within four hours for 52 weeks running.

The charities analysed 41 million A&E attendances from 2010 to 2013 and highlighted a number of contributing factors which could lead to these greater waiting times.

Winter pressures are also associated with higher rates of people waiting for more than four hours, their report states.

They also found that the number of people in emergency departments has risen as the population has grown and aged.

The report suggests that older people are waiting longer than young adults or children. People over the age of 75 spend an average of three and a half hours in A&E compared to two and a half hours for younger patients, they found.

The authors said that elderly people have more complex problems, which often require longer periods of care.

Patients with long-term conditions are also likely to wait longer to be admitted or discharged - and people with more than one of these conditions are forced to wait even longer, they said.

Those who are on the register of a GP surgery with good patient feedback were less likely to attend emergency units.

"We may have reached the limit of what we can deliver with our current A&E capacity," said report author and Nuffield Trust senior research analyst Ian Blunt.

"But without either new money to invest in A&E, or new ways to divert people to other parts of the NHS, rising waits may be inevitable. A lot now rides on NHS England's Urgent and Emergency Care Review.

"The NHS has been criticised for not having the information it needs to fully understand what's going on in A&E. This report provides some of the new evidence we need so that policy-makers are able to target limited resources most effectively.

"However, there's still a lot we don't know. It is vital that the health service makes better use of linked data to understand how issues like bed availability and staffing levels have an impact on what people experience in A&E."

"But the solutions are more complex than simply 'more investment needed', even if that were forthcoming. The access and quality of health and social care available to people outside hospital also needs to be very carefully examined - is it good enough to prevent the need for an A&E visit?

"We also know that hospitals have huge difficulty discharging patients because of a lack of social care. The flow of patients through hospital - to relieve A&E departments and also free up beds - is often disordered and blocked. Only careful attention to all these areas is the solution."

Labour health spokesman Jamie Reed said: "This report is proof that David Cameron's fingerprints are all over the crisis in A&E departments. Patients will be worried to hear things are set to get even worse.

"It is right to warn that older patients are forced to turn to A&E because they simply can no longer get a GP appointment. David Cameron made it harder to see your GP and this scandal is why the next Labour government will guarantee appointments within 48 hours or on the same day for those who need them.

"This report is another reminder for David Cameron that his decimation of England's social care system is leaving older patients trapped in hospital without the support to go home - A&E departments are struggling to cope."

A Department of Health spokesman said: "We know A&Es are experiencing increased demand but the NHS continues to meet its targets and see the vast majority of people quickly.

"We're giving the NHS extra support to keep services sustainable year-round and in the long-term, we want to reduce demand by looking after people better in the community."

The latest figures from NHS England show that for the week ending 13 July, 93.1% of patients attending major "type 1" A&E departments in England spent less than four hours from arrival to admission, transfer or discharge.

Across all types of A&E departments, including those that deal with a single conditions and minor injuries units, the figure was 95.3%.